Single exposure positive-working photopolymer element

ABSTRACT

A high speed, positive-working photopolymer element comprising, in order: (1) a support, (2) a nonphotosensitive layer comprising a hardenable binder (e.g., gelatin) containing a releasable hardener (e.g., glutaraldehyde-bisulfite), and an optional colorant, and (3) a permeable photopolymerizable layer. Imagewise exposure of the photopolymerizable layer is followed by diffusion of an alkali through the nonimage area, releasing the hardener. A subsequent wash-off step produces a positive image of the original.

TECHNICAL FIELD

This invention relates to a low cost, single exposure, aqueousprocessable, positive-working photopolymer element with excellent imagequality suitable for use in electronic imaging, for example, and to anovel imaging process.

BACKGROUND ART

In the electronic imaging field there is a need for convenient and cheapimaging systems. Conventionally, these needs have been met byphotosystems employing silver halide as the photosensitive element. Withthe increasing silver prices, there is need for lower cost systems.Photopolymer elements are now being evaluated in this field. Althoughphotopolymers can be used to produce a satisfactory image, they areconventionally many orders of magnitude slower than representativesilver halide elements and are usually negative-working. If positiveworking, it often requires two exposures. There is a pressing need for acheap, single exposure, positive-working photopolymer element that canbe processed in aqueous solutions to satisfy the needs of the electronicimaging field for example.

BRIEF DESCRIPTION OF THE DRAWING

The invention is illustrated schematically in FIGS. 1-4.

FIG. 1 is a schematic cross-sectional view of the single exposurepositive-working photopolymer element of the invention.

FIGS. 2 and 3 illustrate in section and schematically the exposure anddevelopment of the photopolymer element of FIG. 1.

FIG. 4 illustrates a schematic cross-section of a finished, directpositive image made by the exposure/development sequence of FIGS. 2-3.

SUMMARY OF THE INVENTION

The needs and objects of this invention can be met by providing apositive-working photopolymer element consisting essentially of asupport, on one side of which is coated, in order, (1) anonphotosensitive layer comprising a hardenable binder having areleasable hardening agent mixed therein, and (2) a permeablephotopolymerizable layer.

In an illustrative embodiment the invention is directed to a singleexposure positive-working dual layer photopolymer element consistingessentially of a support, an opaque, nonphotoactive layer comprisingcarbon black, gelatin and glutaraldehyde bisulfite (GDA-HSO₃) on saidsupport, and a photopolymerizable layer coated contiguous thereto. Afterimagewise exposure of the photopolymerizable layer, the photopolymerelement is treated with an aqueous developer solution containing K₂ CO₃/KHCO₃. This solution preferentially diffuses through the unexposedregions of the photopolymerizable layer to the opaque layer, releasingglutaraldehyde, which vary rapidly hardens the surrounding gelatin. Theentire photopolymerizable layer and the unhardened portions of theopaque layer are then removed by washing, leaving a direct positiveimage of the original.

DETAILED DESCRIPTION OF THE INVENTION

It is known that glutaraldehyde will very rapidly harden gelatin,particularly at high pH, but because of its volatility, mobility andreactivity, glutaraldehyde itself would be undesirable in a photographicsystem. However, it reacts with sodium bisulfite to form a stable,crystalline, water-soluble addition product. In the presence ofcarbonate, this reaction is reversed, liberating free glutaraldehyde.

The two-layer structure of the present invention, with aphotopolymerizable layer coated on top of a gelatin layer that containsglutaraldehyde-sodium bisulfite together with a colorant such as carbonblack, is based on this reaction mechanism. But the same principle canbe applied to analogous reactants, as will be further explained.

Referring to the drawings, FIG. 1 shows the positive-workingphotopolymer element of this invention prior to exposure wherein support1 is coated with nonphotosensitive layer 2 comprised of a hardenablebinder containing a releasable hardening agent, and a top layer 3 whichis the permeable photopolymerizable layer, i.e., the imaging layer.

In FIG. 2, the element is being exposed by actinic radiation 4 and 4athrough an image 5. Rays 4 are prevented from striking thephotopolymerizable layer 3 while rays 4a strike said layer, causingphotopolymerization in exposed areas 7. Areas 6 are unexposed, andunpolymerized, and therefore remain permeable.

FIG. 3 shows development by contacting the exposed element with adeveloper liquid 9 which permeates through the unpolymerized areas 6 andcauses the hardening agent in the underlying areas of layer 2 to bereleased, hardening the binder in those areas.

FIG. 4 shows the final, positive image obtained after wash-out of theunhardened areas of layer 2, with the simultaneous removal of all oflayer 3, if desired.

In a preferred embodiment the support 1 is CRONAR polyester, a trademarkof E. I. du Pont de Nemours and Company, Wilmington, Del. for a flexibletransparent polyethylene terephthalate film, which in this case issuitably subbed (subcoated); the nonphotosensitive layer 2 is gelatincontaining carbon black as a colorant for producing a visible image andglutaraldehyde-sodium bisulfite as the releasable hardener; and thepermeable photopolymerizable layer 3 is the negative-working systemdescribed in Bratt et al, "Dot-Etchable Photopolymerizable Elements",U.S. Pat. No. 4,229,517, Example 1. An optional cover sheet may becoated or laminated to photopolymerizable layer 3 to protect it and toprevent oxygen inhibition. An imagewise exposure of this layer 3 to anexposure source rich in ultraviolet radiation will produce image areas 7of polymerized material in the region struck by this radiation. Whencontacted with developer 9, e.g., aqueous Na₂ CO₃, these areas will actas a diffusion resist, i.e., will be slow to diffuse developing agent 9.However, the unexposed and unpolymerized areas 6 will diffuse thedeveloper rapidly into the underlying areas of layer 2, releasing thehardener in these areas and causing crosslinking of the gelatin. Thenoncrosslinked areas can then be washed out with warm water, along withthe imaging layer 3, leaving a colored, positive image on the support.

Suitable supports may be chosen from a wide variety of films composed ofhigh polymers, e.g., polyamides, polyolefins, polyesters, vinyl polymersand cellulosic esters having a variety of thickeners. Also useful aremetal foils, papers and the like. The choice of support is not vital tothis invention although polyethylene terephthalate, suitably subbed toreceive the nonphotosensitive layer, is preferred.

The nonphotosensitive layer is comprised of a hardenable binder whichmay be gelatin (preferred) or such materials as polyvinyl alcohol (PVA),carbamated PVA, polyacrylamide, polyethylene imine, carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC) or mixtures with CMC, etc.Releasable hardeners compatible with the hardenable binder must beselected. For example, glutaraldehyde-sodium bisulfite is particularlyefficacious with gelatin and PVA as well as polyacrylamides andpolyethylene imine.

Other hardeners of gelatin include, for example, glyoxal-sodiumbisulfite, formaldehyde-sodium bisulfite, and starch dialdehyde-sodiumbisulfite (or other alkali metal salts of the above). The organictitanates sold by E. I. du Pont de Nemours and Company, Wilmington, DEas TYZOR, for example, can be used as releasable hardeners for CMC ascan the salts of Cr⁺³. One must also balance the releasing developersolutions with the releasable hardener used so as to get the full effectof this invention. Most of these solutions are aqueous alkalis such asNa₂ CO₃ (sodium carbonate), KOH, NaOH, etc. Other adjuvants may bepresent to help wash out the unhardened portion of this layer and toassist in finally removing all the image-forming photopolymerizablelayer if desired.

A variety of colorants, i.e., pigments and dyes, may be added to thenonphotosensitive layer to provide image coloring if desired. Carbonblack (colloidal carbon) is preferred but other materials such as ironoxide may also be used effectively. They must be compatible with thehardenable binder, however.

Examples of ultraviolet dyes, ultraviolet absorbers, and other dyeswhich can be used in this invention are listed below:

2,2'-dihydroxy-4-methoxy-benzophenone

4-dodecyloxy-2-hydroxybenzophenone

2,4-dihydroxybenzophenone

hydroxyphenylbenzotriazole

2(2'-hydroxy-5'-methoxyphenyl)benzotriazole

resorcinol-monobenzoate

2-hydroxy-4-methoxybenzophenone

2,2'-dihydroxy-4,4'-dimethoxy-benzophenone

2,2',4'-tetrahydroxybenzophenone

2-hydroxy-4-methoxy-benzophenone-5-sulfonic acid (also sodium salt ofabove)

ethyl-2-cyano-3,3-diphenylacrylate

2-ethylhexyl-2-cyano-3,3-diphenylacrylate

    ______________________________________                                        LUXOL ® ORANGE GRL                                                                        Color Index #25 (Solvent Orange)                              LUXOL ® ORANGE GS                                                                         Color Index #24 (Solvent Orange)                              LUXOL ® ORANGE R                                                                          Color Index #20 (Solvent Orange)                              PLASTO ® ORANGE M                                                                         Color Index #21 (Solvent Orange)                              PLASTO ® ORANGE RS                                                                        Color Index #22 (Solvent Orange)                              GRASOL                                                                        Fast Orange 2RN Color Index #33 (Solvent Orange)                              Oil Orange      Color Index #12055 (Solvent                                                   Yellow #14)                                                   Sudan Orange RA Color Index #12055 (Solvent                                                   Yellow #14)                                                   LUXOL YELLOW G  Color Index #45 (Solvent Yellow)                              LUXOL YELLOW T  Color Index                                                   #47 (Solvent Yellow)                                                          PLASTO YELLOW GR                                                                              Color Index #39 (Solvent Yellow)                              PLASTO YELLOW MGS                                                                             Color Index #40 (Solvent Yellow)                              OIL YELLOW 3G   Color Index #29 (Solvent Yellow)                              SUDAN YELLOW    Color Index #30 (Solvent Yellow)                              LUXOL FAST BLUE AR                                                                            Color Index #37 (Solvent Blue)                                LUXOL FAST BLACK L                                                                            Color Index #17 (Solvent Black)                               Primrose Yellow Color Index #77603 (Pigment)                                  Chrome Yellow Light                                                                           Color Index #77603 (Pigment)                                  Chrome Yellow Medium                                                                          Color Index 77600 (Pigment)                                   ______________________________________                                        Dispersed Manganese Dioxide                                                   ______________________________________                                        Toluidine Yellow GW                                                                           Color Index #71680 (Pigment)                                  Molybdate Orange                                                                              Color Index #77605 (Pigment)                                  Dalamar Yellow  Color Index #11741 (Pigment)                                  Green Gold      Color Index #12775 (Pigment)                                  Graphtol Yellow Color Index Pigment Yellow #61                                Graphtol Orange Color Index Pigment Orange #13                                ______________________________________                                    

To obtain an optical density in a thin layer of at least 3.0 throughoutthe 350 to 400 nm region frequently requires a high percentage of dyesand/or pigments, usually between 15-40% by weight, of the hardenablebinder layer.

In photopolymerizable compositions the molecular weight of at least onecomponent of the composition is increased by exposure to actinicradiation, causing a change in the rheological and thermal properties ofthe exposed areas and rendering the exposed areas relatively lesssoluble in solvents than the unexposed areas, thereby producing asolvent-developable image. Photopolymerizable compositions for use inthe invention usually comprise a photoinitiator, an actinic radiationabsorber to opacify layer 2 in the actinic region of the spectrum, aphotopolymerizable monomer, and a polymeric binder, as described furtherbelow.

The photopolymerizable composition contains an organic, free-radicalgenerating system activatable by actinic radiation, i.e., 300 nm andabove, which initiates polymerization of the ethylenically unsaturatedcompound and does not subsequently terminate the reaction. Thefree-radical generating system should have at least one component thathas an active radiation absorption band with a molar extinctioncoefficient of at least about 50 within the range of about 300 to 500nm. "Active radiation absorption band" means a band of radiation whichis active to produce the free radical necessary to initiate thepolymerization. The free-radical generating system can comprise one ormore compounds which directly furnish free radicals when activated byradiation. It can also comprise a plurality of compounds, one of whichyields free radicals after having been caused to do so by a sensitizerwhich is activated by the radiation.

Photoinitiators which can be utilized in the practice of this inventioninclude aromatic ketones such as benzophenone, Michler's ketone(4,4'-bis(dimethylamino)benzophenone),4,4'-bis(diethylamino)benzophenone,4-methoxy-4'-dimethylamino-benzophenone, 2-ethylanthraquinone,phenathraquinone, and other aromatic ketones; benzoin, benzoin esterssuch as benzoin methyl ether, benzoin ethyl ether and benzoin phenylether, methylbenzoin, ethylbenzoin and other benzoins; and2,4,5-triarylimidazole dimers such as2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-(m-methoxyphenyl)imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer,2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer,2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methylmercaptophenyl)-4,4-diphenylimidazole dimer, and the likedisclosed in U.S. Pat. No. 3,479,185, in British Pat. No. 1,047,569(published 1966), and U.S. Pat. No. 3,784,557.

Particularly useful initiators are the 2,4,5-triarylimidazole dimers(also known as hexaarylbiimidazoles). These are used with a free-radicalproducing electron donor agent, such as 2-mercaptobenzoxazole, leucocrystal violet or tri(4-diethylamino-2-methylphenyl)-methane. Suchsensitizers as Michler's ketone may be added. Various energy transferdyes, such as Rose Bengal and Eosin Y, can also be used. Additionalexamples of suitable initiators are disclosed in U.S. Pat. No.2,760,863. Other useful systems employ a triarylimidazole dimer and afree radical producing electron donor agent, with or without the use ofa sensitizing compound as described in U.S. Pat. No. 3,479,185. Anotheruseful group of initiators is those mixtures described in U.S. Pat. No.3,427,161.

The free-radical generating system is employed in a concentrationsufficient to initiate polymerization, which is usually about 0.1-25% byweight based on total composition, and preferably about 2 to 20% byweight.

The instant invention is not limited to the use of any particularpolymerizable monomer, it being required only that the monomer beethylenically unsaturated and capable of addition polymerization. Alarge number of useful monomers is available, generally characterized byone or more terminal ethylenic groups. Among the suitable monomers maybe mentioned various vinyl and vinylidene monomers, e.g., vinylcarboxylates, alpha-alkyl acrylates, alpha-substituted acrylic acids andesters thereof, vinyl ester, vinyl hydrocarbons, acrylic andalpha-substituted acrylic acid esters of the polymethylene glycols andether alcohols, all as disclosed in U.S. Pat. No. 2,760,863 and2,971,504; the various compounds disclosed in U.S. Pat. No. 2,927,022and especially those having a plurality of addition-polymerizationethylene linkages, particularly when present as terminal linkages, andmore especially those wherein at least one and preferably most of suchlinkages are conjugated with a doubly bonded carbon, including carbondoubly bonded to carbon or to such hetero-atoms as nitrogen, oxygen andsulfur; esters of pentaerythritol compounds of the kind disclosed inU.S. Pat. No. 3,261,686; and compounds of the kind described in U.S.Pat. No. 3,380,831; e.g., the reaction product of trimethylolpropane,ethylene oxide, and acrylic and methacrylic acids.

The concentration of the monomer or monomers employed is normally about7.5-35% by weight based on the total solids of the composition, andpreferably between 15-25%.

The binder used in the photopolymer layer is an organic polymericmaterial that is preferably solid at 50° C., and it is necessary thatthe binder be compatible with the polymerizable monomer and thepolymerization initiator system. It is frequently desirable, but it isnot required, that the binder be thermoplastic. The binder may be of thesame general type as the polymerizable monomer being used and may besoluble therein and plasticized thereby.

A wide variety of suitable binders, both thermoplastic andnonthermoplastic, is disclosed in U.S. Pat. No. 3,060,023, e.g.,cellulose ethers or esters; polyalkylene ethers; condensation polymersof glycols with dibasic acids; polymers and copolymers of vinyl esters;acrylic acids and esters; polyvinyl alcohol; cellulose; phenolic resins;and the like. Other binders, including a number of vinylidene polymersare disclosed in U.S. Pat. Nos. 2,760,863 and 2,791,504. Still otheruseful binders are the N-methoxymethyl polyhexamethylene adipamidemixtures of British Pat. No. 826,272, the polyester, polyacetal or mixedpolyesteracetal mixtures of U.S. Pat. Nos. 2,892,716; the fusiblepolyvinyl alcohol derivatives of 2,902,365; the fusible blends ofselected organic-soluble cellulose derivatives of U.S. Pat. No.2,902,365; the fusible blends of selected organic-soluble, base-solublecellulose derivatives of U.S. Pat. No. 2,927,022; the polyvinyl acetalshaving extralinear vinylidene groups of U.S. Pat. No. 2,902,710; thelinear polyamides containing extralinear N-acrylyloxymethyl groups ofU.S. Pat. No. 2,972,540; and the 1,3-butadienes of U.S. Pat. No.3,024,180.

The binder or binder mixture usually comprises 10-75% by weight of thetotal solids.

Particularly preferred as binders are acidic, polymeric, organiccompounds since the photopolymerizable composition resulting isdevelopable in an aqueous alkaline solvent devoid of organic solvents.This is advantageous since organic solvents are costly, may be hazardouswith respect to toxicity and/or flammability, may become scarce due topetrochemical shortages, and may pollute the air and water.

One class of film-forming binders which is soluble in aqueous alkalinemedia and is useful in the compositions of the present invention is madeup of vinyl addition polymers containing free carboxylic acid groups,which are prepared from 30 to 94 mole percent of one or more alkylacrylates and 70 to 6 mole percent of one or morealpha-beta-ethylenically unsaturated carboxylic acids, and morepreferably prepared from 61 to 94 mole percent of two alkyl acrylatesand 39 to 6 mole percent of an alpha-beta-ethylenically unsaturatedcarboxylic acid. Suitable alkyl acrylates for use in preparing thesepolymeric binders include methyl acrylate, ethyl, acrylate, propylacrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butylmethacrylate, etc. Suitable alpha-beta-ethylenically unsaturatedcarboxylic acids include acrylic acid, methacrylic acid and the like.Binders of this type, including their preparation, are described inGerman OLS No. 2,320,849 (published 1973).

The advantages of using acidic binders can also be obtained by selectinga preformed, compatible macromolecular polymeric binding agent which isa copolymer of (1) a styrene-type of a vinyl monomer and (2) anunsaturated carboxy-containing monomer, as described in detail inBritish Pat. No. 1,361,298.

Another preferred photopolymerizable composition is obtained by using apreformed, compatible macromolecular polymeric binding agent mixture,the components thereof taken from two selected classes. The use of themixtures as described in British Pat. No. 1,507,704, eliminates the needfor organic solvents in developing. These are mixtures of two types ofbinders. The first type is preferably selected from a copolymer of vinylacetate and crotonic acid; a terpolymer of ethyl acrylate, methylmethacrylate, and acrylic acid; and cellulose acetate succinate. Thesecond type is preferably selected from toluene sulfonamideformaldehyde; a copolymer of methyl methacrylate and methacrylic acid; aterpolymer of methyl methacrylate, ethyl acrylate, and hydrogen maleate;a terpolymer of vinyl chloride, vinyl acetate, and maleic acid; acopolymer of styrene and maleic anhydride; and a terpolymer of methylmethacrylate, ethyl acrylate, and methacrylic acid.

The nonphotosensitive layer may be coated on the support from anappropriate solvent (e.g. water). After drying, the photopolymerizablelayer is applied from its appropriate solvent. A cover sheet, e.g., athin polyethylene terephthalate sheet sold as MYLAR polyester, atrademark of E. I. du Pont de Nemours and Company, is usually laminatedover the photopolymerizable layer. These steps are all conventional inthe art.

This invention will now be illustrated by the following examples ofwhich Example 1 is considered to be the best mode:

EXAMPLE 1

The following solution is prepared, to make up what the drawingsidentify as layer 2 of this invention:

    ______________________________________                                        Ingredient              Amt. (g.)                                             ______________________________________                                        Distilled Water         130                                                   Gelatin                 2.5                                                   Glutaraldehyde-Sodium Bisulfite                                                                       0.55                                                  Carbon Black (Helioechtschwartz VM).sup.(1)                                                           12.2                                                  ______________________________________                                         .sup.(1) Mobay TM for Pigment Fast Black Carbon Black (35%),                  polyoxyethylene stearyl ether nonionic surfactant (14%), sodium alkylaryl     sulfonate surfactant (10%), methylpentane diol (25%), and water (25%).   

This is coated on 4.2 mil clear polyethylene terephthalate film base (1)which had been coated in a conventional manner with a standardvinylidene chloride, ethyl acrylate, methylmethacrylate sub over which athin substratum of gelatin had also been coated. A 2-mil doctor knife isused to prepare this coating.

The following solution is prepared to make up what the drawings identifyas photopolymerizable layer 3 of this invention:

    ______________________________________                                        Ingredient              Amt. (g.)                                             ______________________________________                                        Methylene chloride      100.0                                                 Polyoxyethylated trimethylolpropane                                                                   4.0                                                   triacrylate (TEOTA)                                                           Michler's ketone, 4,4'-bis(dimethyl-                                                                  0.5                                                   amino)-benzophenone                                                           2-o-chlorophenyl-4,5-di-(M-methoxy-                                                                   1.0                                                   phenyl) imidazolyl dimer (CMD-HABI)                                           SMA-17352A - copolymer of styrene and                                                                 4.0                                                   maleic anhydride esterified with                                              isopropyl alcohol (M. W. 1700, acid                                           number 270) - Arco Chem. Co.                                                  CARBOSET XL-11, an alkali-soluble                                                                     4.0                                                   acrylic resin, (M. W. 40,000, acid                                            number 70, Tg 50-55° C.) - Goodrich                                    Chem. Co.                                                                     FC-430 - a fluorochemical nonionic                                                                    0.2                                                   surfactant, 3M Co.                                                            ______________________________________                                    

This is coated on top of layer 2 made above, using a 2-mil doctor knife.A thin (ca. 0.005 inch) Mylar polyester cover sheet is laminated thereonto protect this element and to prevent oxygen inhibition.

This composite product is exposed through the cover sheet and a negativetest image for about 10 seconds to a 4 kw xenon light source at adistance of 60 inches. The cover sheet is then stripped from the exposedelement and processed in a solution comprising 840 g. K₂ CO and 50 g.KHCO₃ in 16 liters of distilled water. The developing solution diffusesrapidly through the nonimaged areas of the photopolymer film 3 into thecorresponding areas of the black, nonphotosensitive layer 2 underneath.The glutaraldehyde is released in these areas, causing the gelatin tocrosslink and harden. By rinsing in warm water and by gently scrubbingwith a soft material or gauze the photopolymer layer 3 is removed intoto, along with the unhardened portions of the black, nonphotosensitivelayer 2. A high quality positive image of the test image remains. Thisfinal image has a density greater than 3.0 and excellent 5-95% dotfidelity.

EXAMPLE 2

The following solution is prepared to make a photopolymerizablecomposition:

    ______________________________________                                        Ingredient         Amt. (g.)                                                  ______________________________________                                        Methylene chloride 100.0                                                      Methanol           5.0                                                        CARBOSET XL-11 (See Ex. 1)                                                                       4.0                                                        SMA-17352A (See Ex. 1)                                                                           4.0                                                        Water              1.0            Mix before                                                                    charging                                    Potassium Hydroxide                                                                              0.5            to overall                                  Methanol           9.0            mixture                                     CMD-HABI (See Ex. 1)                                                                             1.0                                                        Michler's ketone (See Ex. 1)                                                                     0.5                                                        Trimethylolpropane Triacrylate                                                                   4.0                                                        (TMPTA)                                                                       FC-430 (See Ex. 1) 0.2                                                        ______________________________________                                    

This composition is coated on sample layer 2 made according to theinstructions of Example 1 which had been coated on a polyethyleneterephthalate film support as taught therein. A Mylar polyester coversheet is then laminated over the photopolymerizable layer and anexposure similar to that described in Example 1 is given to thiselement. The cover is then removed and the image developed as inExample 1. A high quality, direct positive image is obtained withexcellent density and dot quality. This example demonstrates the use ofyet another photopolymerizable layer in conjunction with thenonphotosensitive, hardenable layer of this invention.

EXAMPLE 3

The following solution is prepared to make up what the drawings identifyas layer 2 of this invention:

    ______________________________________                                        Ingredient           Amt. (g)                                                 ______________________________________                                        Dist. Water          65                                                       Gelatin              1.25                                                     NaHSO.sub.3          0.1                                                      Glyoxal-sodium bisulfite                                                                           0.275                                                    Helioechtschwartz Carbon Black                                                                     6                                                        (See Ex. 1)                                                                   ______________________________________                                    

This composition is coated on a film support and overcoated with thephotopolymerizable composition of Example 1. A cover layer is appliedand the element is exposed and developed as described in Example 1. Anexcellent, positive image is obtained which indicates thatglyoxal-sodium bisulfite can be used as the releasable hardener in thisinvention.

EXAMPLE 4

The following solution is prepared to make up of an alternate layer 2 ofthis invention:

    ______________________________________                                        Ingredient            Amt. (g.)                                               ______________________________________                                        Distilled Water       100                                                     Polyvinyl alcohol (Vinol ® 107, a                                                               5                                                       fully hydrolysed, low vis. PVA,                                               Air Products & Chem. Co., Inc.)                                               Boric Acid            0.5                                                     Helioechtschwartz Carbon Black                                                                      6                                                       (See Ex. 1)                                                                   ______________________________________                                    

This is coated on a support, overcoated with a photopolymerizable layer,laminated with a cover sheet, exposed and developed as described inExample 1. A fine, high quality direct positive image is obtained whichdemonstrates that polyvinyl alcohol binder and boric acid as thereleasable hardener can be used within the metes and bonds of thisinvention.

EXAMPLE 5

The following solution is prepared to make up another alternate layer 2of this invention:

    ______________________________________                                        Ingredient              Amt. (g.)                                             ______________________________________                                        Distilled Water         65                                                    Gelatin                 1.25                                                  Glutaraldehyde-sodium Bisulfite                                                                       0.24                                                  Acid Violet Dye (4 VNS, Extra Conc.,                                                                  0.40                                                  Sandoz Chem. Co.)                                                             ______________________________________                                    

This material is coated on a polyethylene terephthalate film support asdescribed in Example 1.

The following solution is prepared to make up a photopolymerizablecomposition:

    ______________________________________                                        Ingredient         Amt. (g.)                                                  ______________________________________                                        Methylene chloride 100                                                        Methanol           5                                                          CARBOSET XL-11 (See Ex. 1)                                                                       4                                                          Water              1              Mix before                                  KOH                0.5            charging                                    Methanol           9              overall                                                                       mixture                                     CMD-HABI (See Ex. 1)                                                                             1                                                          Michler's ketone (See Ex. 1)                                                                     0.5                                                        TMPTA (See Ex. 2)  2                                                          TEOTA (See Ex. 1)  2                                                          FC-430 (See Ex. 1) 10             drops                                       ______________________________________                                    

This composition is overcoated on layer 2 made above, using a 2 mildoctor knife, and dried. A polyethylene terephthalate cover sheet islaminated over this structure. The photopolymer element is exposed anddeveloped as described in Example 1. A high quality, dark violet, directpositive image is obtained.

EXAMPLE 6

The following solution is prepared to make up another layer 2 of thisinvention:

    ______________________________________                                        Ingredient          Amt. (g.)                                                 ______________________________________                                        Distilled Water     130                                                       Gelatin             2.5                                                       Glyoxal-sodium Bisulfite                                                                          0.52                                                      Dalamar Yellow (C. I. Pigment                                                                     12.0                                                      Yellow 74, 20% Disp. in H.sub.2 O)                                            ______________________________________                                    

This composition is coated on a copper surface of a copper/epoxylaminate board and dried. The photopolymerizable composition fromExample 5 is applied over this layer, dried and a conventional coversheet applied thereon. The composition element is exposed and developedas described in Example 1. A yellow positive image on the copper layeris obtained. The image is then etched with 39° Baume ferric chloride at130° F. to remove the copper in the nonimage area, showing that properlyused, this element will function as a photoresist.

EXAMPLE 7

The following solution is prepared to make up another layer 2 of thisinvention:

    ______________________________________                                        Ingredient           Amt. (g.)                                                ______________________________________                                        Distilled Water      65                                                       Gelatin              1.25                                                     Propylene glycol alginate                                                                          0.3                                                      releasable hardener.sup.(1)                                                   Helioechtschwartz Carbon Black                                                                     6                                                        (See Ex. 1)                                                                   ______________________________________                                         .sup.(1) propylene glycol ester of alginic acid                               ##STR1##                                                                      sold as KELCOLOIDO, a trademark of Kelco Co. (When this material              hydrolyses at pH 7 or greater, the products will rapidly harden gelatin       see U.S. Pat. No. 3,378,373.)                                            

This material is coated on a support as described in Example 1 anddried. A photopolymerizable layer made as described in Example 1 iscoated over this layer, dried and a conventional cover sheet appliedthereon. This composite structure is exposed and developed as describedin Example 1. An excellent, high quality direct positive image with gooddensity and dot quality is achieved. In an alternate developing method,another sample of the composite described in this example is exposed andsimply processed by dipping for 25 seconds in a 1% KOH solution at 75°F. and rinsed under 100° F. water. The resulting product was a superiordirect positive image with high density and excellent dot quality.

EXAMPLE 8

The following solution is prepared to make up another layer 2 of thisinvention:

Mix 10 g. of hydroxyethyl cellulose (CELLOSIZE WP-09-H, trademark ofUnion Carbide Co.) in 400 g. H₂ O in a blender for 40 mins.

    ______________________________________                                        Ingredient           Amt. (g.)                                                ______________________________________                                        Solution from above  20                                                       Glutaraldehyde Sodium Bisulfite                                                                    0.2                                                      Helioechtschwartz Carbon Black                                                                     5                                                        (See Ex. 1)                                                                   ______________________________________                                    

This material is coated on a suitable support as described in Example 1.A photopolymerizable layer made according to Example 1 is applied overthis dried layer and a conventional cover sheet laminated thereon. Thecomposite product is exposed as described in Example 1 and developed bywashing in 5% alcoholic KOH at 75° F. and 100° F. water washing. Asuitable direct positive image is obtained.

EXAMPLE 9

The following solution is prepared to make layer 2 of this invention:Mix 2.5 g. carboxymethyl hydroxyethyl cellulose (Hercules Chem. Corp.type 37M) in 100 g. H₂ O in a blender for 40 mins.

    ______________________________________                                        Ingredient           Amt. (g.)                                                ______________________________________                                        Solution from above  20                                                       Glyoxal Sodium Bisulfite                                                                           0.2                                                      Helioechtschwartz Carbon Black                                                                     5                                                        (See Ex. 1)                                                                   ______________________________________                                    

This material is coated on a support, dried, a photopolymerizable layerapplied thereon, followed by drying and lamination of a cover sheet allas described in Example 1. The composite product is exposed as describedin Example 1 followed by development in 5% alcoholic KOH and waterwashing at 100° F. A suitable direct positive image is obtained.

EXAMPLE 10

The following solution is prepared to make up a layer 2 of thisinvention: Mix 2.5 g. carboxymethyl cellulose, sodium salt (Du Pont Co.,Grade R-755-H) in 200 g. H₂ O-pH 6.4

    ______________________________________                                        Ingredient           Amt. (g.)                                                ______________________________________                                        Solution from above  20                                                       N,N'--methylenebisacrylamide                                                                       0.1                                                      releasable hardener                                                           Helioechtschwartz Carbon Black                                                                     4                                                        (See Ex. 1)                                                                   ______________________________________                                    

This is coated on a support, dried, overcoated with photopolymerizablecomposition, dried, and a cover sheet laminated thereto as described inExample 1. The composite product is exposed as described in Example 1and developed by 5% alcoholic KOH (2 mins. at 75° F.) and water washingin 100° F. water. A suitable direct positive image is obtained.

EXAMPLE 11

The following solution is prepared to make up a layer 2 of thisinvention:

    ______________________________________                                        Ingredient           Amt. (g.)                                                ______________________________________                                        Solution from Ex. 10 20                                                       Aqueous soln. containing 0.1 g.                                                                    10                                                       CrK (SO.sub.4).sub.2.12 H.sub.2 O + 0.1 g.                                    0.2N H.sub.2 SO.sub.4                                                         Helioechtschwartz Carbon Black                                                                     4                                                        ______________________________________                                    

This is coated on a support, dried, overcoated with photopolymerizablesolution, dried, and a cover sheet laminated thereto as described inExample 1. The composite product is exposed as described in Example 1and developed by 5% alcoholic KOH at 75° F. followed by washing in waterat 100° F. A suitable direct positive image is obtained.

I claim:
 1. A positive-working photopolymer element consistingessentially of a support, on one side of which is coated, in order, (1)a nonphotosensitive layer comprising a gelatin binder, a colorantselected from the group consisting of pigments and dyes, and a sodiumbisulfite adduct of a gelatin hardening agent of the group consisting ofglutaraldehyde, glyoxal, formaldehyde, and starch dialdehyde and (2) aphotopolymerizable layer comprising a photoinitiator, an actinicradiation absorber, a photopolymerizable monomer, and a polymericbinder.
 2. The photopolymer element of claim 1 wherein thenonphotosensitive layer (1) is opaque and the colorant is carbon black.3. The photopolymer element of claim 1 wherein the support is apolyethylene terephthalate film.
 4. The photopolymer element of claim 1wherein the photopolymerizable layer (2) comprises a photoinitiator, anactinic radiation absorber, a photopolymerizable monomer, and apolymeric binder.
 5. The photopolymer element of claim 1 wherein thephotopolymerizable monomer is a member selected from the groupconsisting of triethyleneglycol dimethacrylate (TDMA), andpolyoxyethylated trimethylolpropane triacrylate (TEOTA).